add SO_TYPE query to the portable Eio socket interface

lib_eio/mock/sockopt.ml

@@ -21,6 +21,7 @@ let default (type a) (opt : a Eio.Net.Sockopt.t) : a =
   | SO_LINGER -> None
   | SO_RCVTIMEO -> 0.0
   | SO_SNDTIMEO -> 0.0
+  | SO_TYPE -> `Stream
   | _ -> raise (Eio.Net.err Invalid_option)
 
 let getsockopt : type a. string -> a Eio.Net.Sockopt.t -> a = fun label opt ->

lib_eio/net.ml

@@ -214,6 +214,14 @@ module Sockaddr = struct
       Format.fprintf f "udp:%a:%d" Ipaddr.pp_for_uri addr port
 end
 
+type socket_type = [ `Stream | `Dgram | `Raw | `Seqpacket ]
+
+let pp_socket_type f = function
+  | `Stream -> Fmt.string f "stream"
+  | `Dgram -> Fmt.string f "dgram"
+  | `Raw -> Fmt.string f "raw"
+  | `Seqpacket -> Fmt.string f "seqpacket"
+
 module Sockopt = struct
   type _ t = ..
 
@@ -264,6 +272,7 @@ module Sockopt = struct
     | SO_LINGER : int option t
     | SO_RCVTIMEO : float t
     | SO_SNDTIMEO : float t
+    | SO_TYPE : socket_type t
 
   type _ t +=
     | TCP_CORK : bool t
@@ -312,6 +321,7 @@ module Sockopt = struct
       | SO_LINGER -> Some ("SO_LINGER", Fmt.(option ~none:(any "<none>") int))
       | SO_RCVTIMEO -> Some ("SO_RCVTIMEO", Fmt.float)
       | SO_SNDTIMEO -> Some ("SO_SNDTIMEO", Fmt.float)
+      | SO_TYPE -> Some ("SO_TYPE", pp_socket_type)
       | TCP_CORK -> Some ("TCP_CORK", Fmt.bool)
       | TCP_KEEPIDLE -> Some ("TCP_KEEPIDLE", Fmt.int)
       | TCP_KEEPINTVL -> Some ("TCP_KEEPINTVL", Fmt.int)

lib_eio/net.mli

@@ -156,6 +156,12 @@ type 'a t = 'a r
 
 (** {2 Socket options} *)
 
+type socket_type = [ `Stream | `Dgram | `Raw | `Seqpacket ]
+(** The communication semantics of a socket. *)
+
+val pp_socket_type : socket_type Fmt.t
+(** [pp_socket_type] formats a {!socket_type} for display. *)
+
 module Sockopt : sig
   (** An extensible type for socket options. Portable options can be defined
       here, while platform-specific options can be added by backends.
@@ -186,6 +192,7 @@ module Sockopt : sig
     | SO_LINGER : int option t  (** Linger on close if data present *)
     | SO_RCVTIMEO : float t     (** Receive timeout *)
     | SO_SNDTIMEO : float t     (** Send timeout *)
+    | SO_TYPE : socket_type t   (** Get the socket type (read-only) *)
 
   (** {2 Linux-specific options} *)
 

lib_eio/unix/eio_unix_stubs.c

@@ -405,3 +405,30 @@ CAMLprim value caml_eio_sockopt_string_get(value v_fd, value v_id) {
   v_result = caml_alloc_initialized_string(slen, buffer);
   CAMLreturn(v_result);
 }
+
+CAMLprim value caml_eio_unix_so_type(value v_fd) {
+  CAMLparam1(v_fd);
+  int ty;
+  socklen_t optlen = sizeof(ty);
+  #ifdef _WIN32
+  SOCKET sock = Socket_val(v_fd);
+  if (getsockopt(sock, SOL_SOCKET, SO_TYPE, (char *)&ty, &optlen) != 0) {
+    caml_win32_maperr(WSAGetLastError());
+    caml_uerror("getsockopt", Nothing);
+  }
+  #else
+  int sock = Int_val(v_fd);
+  if (getsockopt(sock, SOL_SOCKET, SO_TYPE, &ty, &optlen) != 0)
+    caml_uerror("getsockopt", Nothing);
+  #endif
+  switch (ty) {
+    case SOCK_STREAM:    CAMLreturn(caml_hash_variant("Stream"));
+    case SOCK_DGRAM:     CAMLreturn(caml_hash_variant("Dgram"));
+    case SOCK_RAW:       CAMLreturn(caml_hash_variant("Raw"));
+  #ifdef SOCK_SEQPACKET
+    case SOCK_SEQPACKET: CAMLreturn(caml_hash_variant("Seqpacket"));
+  #endif
+    default:             caml_invalid_argument("Eio_unix: unrecognised SO_TYPE");
+  }
+  CAMLreturn(Val_unit); /* unreachable */
+}

lib_eio/unix/primitives.h

@@ -25,4 +25,5 @@ CAMLprim value caml_eio_sockopt_int_set(value, value, value);
 CAMLprim value caml_eio_sockopt_int_get(value, value);
 CAMLprim value caml_eio_sockopt_string_set(value, value, value);
 CAMLprim value caml_eio_sockopt_string_get(value, value);
+CAMLprim value caml_eio_unix_so_type(value);
 CAMLprim value eio_unix_is_blocking(value);

lib_eio/unix/private.ml

@@ -94,6 +94,7 @@ external setsockopt_int : Unix.file_descr -> Sockopt.t -> int -> unit = "caml_ei
 external getsockopt_int : Unix.file_descr -> Sockopt.t -> int = "caml_eio_sockopt_int_get"
 external setsockopt_string : Unix.file_descr -> Sockopt.t -> string -> unit = "caml_eio_sockopt_string_set"
 external getsockopt_string : Unix.file_descr -> Sockopt.t -> string = "caml_eio_sockopt_string_get"
+external so_type : Unix.file_descr -> Eio.Net.socket_type = "caml_eio_unix_so_type"
 
 let err_run_sock fn x =
   try fn x
@@ -207,6 +208,7 @@ let setsockopt : type a. Fd.t -> a Eio.Net.Sockopt.t -> a -> unit = fun fd opt v
     | Eio.Net.Sockopt.SO_LINGER -> Unix.setsockopt_optint fd Unix.SO_LINGER v
     | Eio.Net.Sockopt.SO_RCVTIMEO -> Unix.setsockopt_float fd Unix.SO_RCVTIMEO v
     | Eio.Net.Sockopt.SO_SNDTIMEO -> Unix.setsockopt_float fd Unix.SO_SNDTIMEO v
+    | Eio.Net.Sockopt.SO_TYPE -> invalid_arg "SO_TYPE is a read-only socket option"
     | Net.Sockopt_bool bo -> Unix.setsockopt fd bo v
     | Net.Sockopt_int bo -> Unix.setsockopt_int fd bo v
     | Net.Sockopt_optint bo -> Unix.setsockopt_optint fd bo v
@@ -286,6 +288,7 @@ let getsockopt : type a. Fd.t -> a Eio.Net.Sockopt.t -> a = fun fd opt ->
     | Eio.Net.Sockopt.SO_LINGER -> Unix.getsockopt_optint fd Unix.SO_LINGER
     | Eio.Net.Sockopt.SO_RCVTIMEO -> Unix.getsockopt_float fd Unix.SO_RCVTIMEO
     | Eio.Net.Sockopt.SO_SNDTIMEO -> Unix.getsockopt_float fd Unix.SO_SNDTIMEO
+    | Eio.Net.Sockopt.SO_TYPE -> so_type fd
     | Net.Sockopt_bool bo -> Unix.getsockopt fd bo
     | Net.Sockopt_int bo -> Unix.getsockopt_int fd bo
     | Net.Sockopt_optint bo -> Unix.getsockopt_optint fd bo

tests/network.md

@@ -579,6 +579,7 @@ Test portable socket options on a TCP socket:
 # run @@ fun ~net sw ->
   let server = Eio.Net.listen net ~sw ~reuse_addr:true ~backlog:5 addr in
   let client = Eio.Net.connect ~sw net (Eio.Net.listening_addr server) in
+  try_getsockopt client Eio.Net.Sockopt.SO_TYPE;
   Eio.Net.setsockopt client Eio.Net.Sockopt.TCP_NODELAY true;
   assert (Eio.Net.getsockopt client Eio.Net.Sockopt.TCP_NODELAY);
   Eio.Net.setsockopt client Eio.Net.Sockopt.SO_KEEPALIVE true;
@@ -592,6 +593,7 @@ Test portable socket options on a TCP socket:
   Eio.Net.setsockopt client Eio.Net.Sockopt.SO_RCVTIMEO 5.0;
   let timeout = Eio.Net.getsockopt client Eio.Net.Sockopt.SO_RCVTIMEO in
   traceln "SO_RCVTIMEO: %.1f seconds" timeout;;
++SO_TYPE = stream
 +SO_SNDBUF: positive
 +SO_LINGER = 10
 +SO_RCVTIMEO: 5.0 seconds
@@ -614,8 +616,10 @@ Test socket options on datagram socket:
 ```ocaml
 # run @@ fun ~net sw ->
   let udp = Eio.Net.datagram_socket net ~sw `UdpV4 in
+  try_getsockopt udp Eio.Net.Sockopt.SO_TYPE;
   Eio.Net.setsockopt udp Eio.Net.Sockopt.SO_BROADCAST true;
   try_getsockopt udp Eio.Net.Sockopt.SO_BROADCAST;;
++SO_TYPE = dgram
 +SO_BROADCAST = true
 - : unit = ()
 ```